Protective device for electric circuits.



A: 0. EASTWOOD. PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

APPLICATION FILED NOV. 23, 190B.

Patented May 25, 1909,

ap aratus.

a adapted to span two sets of which inevitably occurs when the circuit is blow-out coil being effective in disruptin ARTHUR c. EASTWOOD,

OF CLEVELAND, OHIO.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

Specification of Letters Patent.

Patented May 25, 1909.

Application filed November 23, 1908. Serial No. assess.

To all whom it may concern:

Be it known that I, Anrnun O. EASTWOOD, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented or discovered new and useful Improvements in Protective Devices for Electric Circuits, of which the following is a specification.

M inventionmelates to new and useful com inations of devices for the protection of electric circuits, plarticularly electrical circuits containing t e windings of an electric motor.

The objects of my invention are: let. To produce a simple and reliable combination of parts which will-automatically open an electric circuit upon the occurrence of no voltage or of an abnormally low voltage and will not again permit the closing of the circuit until the re uisite amount of resistance has been again included therein. 2nd. To provide an arrangement of parts which will auto matically open the circuit in case of an abnormal flow of current therein and which will not again permit the closing of the circuit until the requisite resistance has been again reinserted in the circuit. 3rd. To provide means whereby the circuit may be readily opened from a distance with very simple and inexpensive additions to the The accompanying drawing illustrates diagrammatically my invention applied to a motor starter or speed controller used in connection with a compound wound motor.

In this drawing a is a knife switch connected to a source of current sup ly.

O is the starter or controlling evice comprising an arm A carrying a contact brush concentrically The segments 1 to 12, inclusive, of the outer group are connected to various points in the bank of resistance R. The inner segment 13 is connected to one side of a knife switch a through the wire 16. The shorter inner segment 14 is electrically connected to the inner segment 13, this shorter segment being added for the sake of cheaper renewal when the contact becomes roug ened through the action of the are arranged segments.

opened. The wire 16 is connected to the segment 13 through the winding of a blowout coil B, the magnetic field set up by this the arcs former when the circuit is opened wound magnet? (The other end of this brake winding is connected to the armature G through the wire 18 and the other end of the armature connects through the .wire 19 with the winding of an overload coil or relay 0 which in turn is connected to Contact 8 of the magnetically-closed switch S, the other main contacts of which is connected through the wire 15 to the negative side of the knife switch 8. It will, therefore, be seen that the contacts 8 and s of the magnetically-closed switch S are in series with the main circuit and this main circuit cannot be established until switch S is closed. The switch S is designed to open through the action of ravity or a combination of gravity an the spring a when its coil is deenergized orjar tially denergized through an abnormal in voltage.

Assumingthe sw'tch S to be closed and the arm A of the centre ler C to be so moved that the biush'c s ans contacts 1 and 13, the main circuit will t ien be as follows: from the plus side of the switch 8, through the wire 16, the

blow-out coil B, the contact 13, the brush a, contact 1, all of the resistance R, the wire 17, the series field F of the motor, the series winding D of the brake, the wire 18, the armature G of the motor, the wire 19, the winding of the relay 0, the contacts a and s of the switch S, and the wire 15 to the negative side of switch 8, thus completing the circuit. The motor will then run at minimum speed. This speed will be gradually increased, if the arm Abe advanced toward the full-on position until when the contact 12 is reached, the resistance R will all be 'cut out and the motor should operate at full speed. If while the motor is running, the voltage of the circuit should fail or should become ab normally low, the switch S will, as I will presently show, automatically opengthe arm A of the controller 0 remaining in the posi tion in which'it had been previously lel't. Should now the voltage of the circuit he suddenly reestablished, the switch S will not at once close and in fact, cannot be closed until the arm A is brought to the off-position so that all of the resistance R must be in the motor circuit when the switch S closes. it will be seen that one end of the winding 1/) of switch S is, connectedthrough the wire 26,

the contacts of the relay() and the wire 27 to contact 13 of the controller 0. The switch S carries an auxiliary contact comprised by a disk or metallic bridging member T which Y connects together the stationary contacts 6',

i i when the switch S is open. The remaining end of the winding w of switch is connected to the auxiliary contact 25', which is connected to the auxiliary contact 75 a re- 0 wire or the negative side of the switch 8.

close.

I The contact't is connected through-the wire 25 to the last contact 12 of the outer group of contacts of the controller 0. Y

With the arm A of the controller 0 in any but the off-position, it will be seen that the effect is to connect both ends of the winding of the switch S to the same side of the circuit. No current can then flow through the winding of theswitch S and the switch will not Following. out these connections it will be seen that one end of the winding of I the switch S is connected through the wire 26,- the contacts of relay 0 and the wire 27 to thecontact 13 which in'turn is connected to the positive main through-the blow-out coil B and theuwire'lfi, lh'ei'other end of the minding of coil S will also be connected to the ositive main througlr thc" contact 2, the

' ridging member T, theclontact t the wire 4O 25, which is also connected "to the positive main through the brush? ,Ethe co tact 13, the winding of the blow o'ut'coil] and the wire 16, when the\ arm of thecontroller is in any but the "off-position "when the arm A is returiiedto the off *osition, current then kv the contacts of the relay 0, the .wire 26, the

winding w of the switch S, the auxiliary contact If, the auxiliary contact t, the resistance r, the wire 23, the switch it (as-' summg the-switch h'to he closed) and the wire 22 to the negative side of the switch 8.

:This completes the circuit through the winding of the switch S and causes the switch; to close. The inctor may then be safely started. as before by advancing the arm of the controller C so as to cut out the resistance R gradually. In case the armof the controller should be advanced'too rapidly so as to cause the motor to draw excessive current, or in case the mtitoi should be over- (55 loaded from any other cause, the relay,(),

the windin of which carries the full motor current, wil raise its plunger, thus separating the auxiliary contacts 0. It will be seen that this interrupts the circuit of the winding of the switch S since one end of the winding will bethereby disconnected from the, wire 27 the contact 13 and the wire 16, through which it is normally connected to the positive side of the switch 8. The switch S will then openand cannot again be closed until thearm A is again returned to the off-position, at which time the switch S will automatically close and the motor may be again started in the usual way. It will be seen also that the switch it is in the circuit of therwinding of the switch S, so that, if at any time the switch h is opened, the switch S will open thus opening the main motor circuit. Even if the .switch it be closed, the arm A of the controller C must be returned to the elf-position before switch S can again close. The switch it can be placed at any desired distance from themotor and controller and, of course, a number of such switches can be connected in series so that the motor can be readily stopped from a number of different points. Since the switch it and connecting wires leading to it have to carry only, the very small currents required by the winding of the switch S, such switches may be installed in desired places and in the most convenient number with very littlev addition to the cost of installation.

It is to be observed that the arrangement requires no additional or special contacts to the controlling switch 0 in view of which the safety features embodied in my invention may be readily applied to existing controlling switches not specifically designed with such protective features in view.

It will be understood that my invention embodies means for automatically opening the motor circuit in cases of under-voltage, no voltages, overload and also from .a dis tance b 1 the manual opening of a switch and that, w en the circuit is opened under any of these conditions, the circuit is held open unlll) til all of the starting resistance is inserted in the circuit by moving the arm A of the controller C to the ofi-position, at which time the magnetically operated switch automatically I closes.

L cla1m- 1, In combination an electric motor, a conand means for short circuiting said magnetizing winding when said main switch is open and said controlling switch is in any but the starting position, the short circuit around said magnetizing winding being opened when thecontrolling switch is brought to the oilposition.

through. the contacts. of said controlling switch when said magnetically-closed switch is open and the controlling switch is in any but the oil-position.

4. In. combination a controlling switch, a magnetically-closed switch having its main contacts in the circuit governed by said controlling switch, a windin g for said magnetically-closed switch, one end of said winding being connected to the line contact of said controlling switch, the other end of said wind ing being connected to the other side of the line through a'resistan ce and an auxiliary switch carried by said magnetically-closed switch and closed when said magnetic switch is open, the contacts of said auxiliary switch connecting the second end of the winding of said magnetically-closed switch to the same side of the line to which the other end of said winding is connected so long as the controlling switch is in any but the off-position.

5. In combination a controlling switch for an electric circuit, a magnetically-closed main switch having its main contacts in the circuit to be controlled, a magnetizing winding for closing said main switch, wmncc cions between the ends of said magnetizing winding and the contacts of said controlling switch whereby both ends of said winding are connected to the same side of the supply cirrnain switch having its main contacts in th circuit to be controlled, a magnetizing windlng for closing said main switch, connections between the ends of said magnetizing winding and the contacts of said controlling;

switch whereby both ends of said winding are connected to the same side of the supply circuit when the controlling switch is in an y' but the off-position and said main switch is open, a relay havin its winding in the circuit to be controlled anr contacts in the circuit of the winding of said main switch, and a manually-operated switch also in the circuit of the magnetizing winding of said main switch. Signed at'Clevcland, Ohio, 1. his Bin-h day of November, 1908.

Vitnesses:

HARRY 'l. STnA'rroN, H; M. DIEMER. 

